


Five Times Rin’s Genetic Makeup was in Question (And One Time it Mattered)

by notanightlight



Category: Free!
Genre: Gen, Matsuoka Rin's Teeth, Minor Injuries, Platonic Relationships, Reference to the West Australian shark cull of 2014, Rin May or May Not Be a Shark-Boy, Samezuka Swimmers show up here and there, Season 2 compliant, Shark Behavior, Team Bonding, Team as Family, because I started this that long ago, joint practice
Language: English
Status: Completed
Published: 2020-06-13
Updated: 2020-06-13
Packaged: 2021-03-04 03:46:50
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,613
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24667084
Author URL: https://archiveofourown.org/users/notanightlight/pseuds/notanightlight
Summary: Rin isn’t actually a shark, or is he?
Relationships: Hazuki Nagisa & Matsuoka Rin & Nanase Haruka & Ryuugazaki Rei & Tachibana Makoto, No Romantic Relationship(s)
Comments: 7
Kudos: 14





	Five Times Rin’s Genetic Makeup was in Question (And One Time it Mattered)

**Author's Note:**

> This has been languishing in my WIP folder since 2014. I think I started it in response to a prompt on an anon meme, but I can’t remember for sure. I also can’t remember if I posted the first few parts on that anon meme or not. Either way, I went in, cleaned up what was already done, and wrote the last few scenes. Much thanks to my beta reader, Squickymuse! 
> 
> Enjoy you future fish!

  
  


**1\. Circling:**

**  
** The first time someone really commented on Rin’s somewhat fishy behavior, they were only joking.

The Iwatobi swimmers were in the swimwear store, looking for some new goggles when an excited cry of, “Gou-san!” alerted them to the presence of the Samezuka swim team. Momotarou was about as far from unnoticeable as humanly possible, especially around his crush. Thankfully for Gou’s sake, Momotarou’s excited chatter was cut short by a well executed headlock and terse instructions to go try on some suits.

She breathed a sigh of relief as her aspiring suitor walked off with a whine. There were perks to your big brother being the captain.

Rin just huffed and shook his head, mumbling, “Someday I’ll come up with a training regimen that will actually wear him out,” under his breath. Instead of following his teammate, he decided to take the opportunity to catch up with Gou. They chatted about the various going’s ons at their schools, festival plans, and a bit of sibling gossip. All the while the Iwatobi team scoped out the bogglingly big selection in the goggle section.

Subtly, with the cunning all younger siblings inevitably develop, Gou began herding her brother towards her team. As soon as she deemed they were in range, she stepped back to observe. Just as she predicted, Rin continued on to the goggles, absentmindedly looking them over.

With a sharp movement, she cut into an argument between Rei and Nagisa over the merits of various goggle brands.

“Just watch,” she told them, nodding to where Rin was cruising along the displays.

“Oh, did you ask Rin for advice?” Makoto asked, with Haru watching the scene with his usual unperturbed expression from over his shoulder.

“No need.” She pointed dramatically to a particular display that Rin was slowly circling, observing from all angles, “Those are the ones we need. He always gravitates towards the thing he’s the most interested”

Rin’s head snapped up at a call of, “Rin-senpai! Rin-senpai! Checkout this suit!” and he diverted his course towards the fitting rooms, not even breaking his stride.

While the others began gathering the unwittingly-Rin-approved goggles, Nagisa watched as Rin began assessing the suits his teammates had chosen. The redhead walked around each team member in slow circles, commenting and either sending them to purchase their suit or go try on another.

With a giggle, Nagisa elbowed Rei. “Look! Rin-chan looks like some kind of shark!”

“Sharks don’t really circle their prey,” Makoto interjected, “Do they?”

Nagisa debated this with him until they left the store, but dropped the subject afterwards. Despite this, Rei found himself checking out a book on shark behavior the next day.

It turned out that sharks do not circle their prey to attack, but do circle if they find something curious or interesting. 

Curious.

  
  


**2\. Scenting blood:**

The second time anyone pointed it out, it wasn’t a joke. 

It happened during a joint practice at Samezuka. It was only a quarter of the way into practice when Rin suddenly held up a hand, forestalling the conversation he had been having with Makoto. To Makoto’s confusion, Rin closed his eyes and sniffed the air, before sweeping his eyes over the pool.

“Uozumi,” he called to the dark haired swimmer treading water on the other side of the pool, “Out of the pool.”

The other boy appeared surprised, but complied, wincing as he stepped out onto solid ground. Rin swam over and pulled himself out of the water.

“Let me see your foot,” he said. The rest of the pool had gone quiet, watching as Uozumi picked up his foot. A trickle of blood was seeping out of a cut in the bottom of it. 

“Go to the nurse,” Rin told him before addressing the rest of the room, “I want everyone to put on shoes. It looks like there may be some broken glass so be careful where you step.”

After shoes were carefully retrieved, the two teams swept the pool area until all shards of glass had been found. Apparently, someone had been a bit careless when they were changing one of the overhead lights and hadn’t cleaned up properly.

“How did Rin-chan know Uozumi was bleeding from the other side of the pool?” Nagisa asked Makoto as they returned their shoes to the locker room.

Makoto shrugged. “I don’t know,” he admitted, “We were just talking and then he just...” Makoto chuckled a bit self consciously. “Well, it sounds strange, but it looked like he smelled it.”

Rei contemplated this in silence before tentatively adding, “You know, sharks can smell blood in the water from miles away.”

“But Rin’s not a shark,” Makoto countered. He looked over at Haruka, “Right?”

Haru just shrugged and walked back into the pool.

What did that matter when there was a pool waiting?

Still, even he couldn't help but notice that Rin wrinkled his nose every time he dove into the water.

  
  
  
  


**3\. The Teeth:**

The third time, it got much harder to pass things off as coincidence. 

They were just fooling around over the weekend, trying to relax before the end of the year started closing in. They had already played video games at Makoto’s house, stopped for icecreams, and kept Haru from jumping into the fish tank at the local pet store. After that, they decided it was best to head to the swim club.

Nagisa was taking the walk as an opportunity to have Rin show him how to use his longboard. (He had insisted that Rin bring it along after Gou mentioned that he’d picked it up while in Australia). Thus far he had learned how to push, brake, and steer with modest success. 

Rin was currently on the board, trying to teach him how to pump. The red head was rocking his body as he propelled himself along, making it look so much easier than it had been when Nagisa tried. He was just explaining how to shift a person’s center of gravity, which had Rei nodding along even though he had no intention of trying the longboard himself, when a cat darted into his path.

What happened next was like something out of a bad slapstick comedy sketch.

Rin swerved to avoid the cat, which sent him to the side of the road. The longboard’s wheels caught on the loose gravel and sent Rin flying over the front, where he crashed face first into some metal railing. His shout startled the cat which darted between Makoto’s legs as it frantically raced away from the commotion. This caused Makoto to yelp in surprise and chuck the water bottle he had been drinking from. 

When the shouting was all over with, Makoto, Haruka, and Rei were soaked, Rin was groaning on the ground, and the longboard rolled back to stop against Nagisa’s feet with a gentle bump. There was a disbelieving sort of stillness for a moment before they all rushed as one to where Rin was lying on the ground.

“Rin! Are you alright? What hurts?”

Rin had a hand protectively covering his mouth, but it did little to hide the blood dripping down his chin or the tears that had welled up in the corners of his eyes. 

“My mouth,” he replied in a muffled voice.

Makoto gently coaxed his hand away from his mouth and looked over the damage. Rei hissed through his teeth at the sight of the gash in Rin’s lip where his teeth had torn into it. 

“That looks pretty bad,” Makoto said, pulling a slightly damp tissue out of his pocket to clean up the blood.

“I think…” Rin said slowly, with a thoughtful expression, “Did one of my teeth get knocked out?” 

He opened his mouth and carefully ran his tongue along his top row of teeth, until it came to a gap on the left side. He winced as he prodded the bleeding space where a tooth used to be.

“Oh no no no no no,” Nagisa cried, beginning to frantically search the ground, “We’ve gotta find it! They can put it back if we find it, right!”

“Right,” Rei replied, joining the search.

“You two keep looking,” Makoto said, pulling Rin to his feet, “Haru and I will get Rin to a doctor.”

Rin needed a few stitches for the gash in his lip, but the missing tooth couldn’t be found.

It wasn’t until two weeks later, when Rin greeted them with a big toothy grin at the first joint practice since he got his stitches out that they realized anything out of the ordinary had happened. 

“I’m glad Rin’s tooth was fixed,” Rei commented.

“Yeah,” Nagisa agreed, “I wonder how they did it without the tooth.”

“Maybe he regrew it,” Haruka suggested to everyone’s surprise.

“I don’t think people can do that.”

Haru just shrugged, “Sharks can”

“Do- do you really think Rin-chan-san is some kind of shark person?”

“What if he got bit by a radioactive shark and got shark powers or something?” Nagisa added.

Makoto watched Rin congratulate one of his teammates on a personal best with a grin that displayed a complete set of teeth.

“...or something,” he murmured.

  
  
  
  


**4\. 6th Sense:**

By the time the fourth questionable clue came around, the whole Iwatobi swim team were on high alert. Rei’s big book of sharks was a constant companion, frequently referenced to see how Rin’s behaviors matched up. Therefore, this particular clue was less of a single incident and more of a collection of observations.

Rei was the first to point something out. He happened to notice that Rin was preternaturally good at avoiding Nagisa’s sneak attacks. He found this particularly impressive because he, of all people, knew just how difficult it could be to shake Nagisa when the bubbly boy had decided to stick to you.

Rei’s realization prompted Haruka to share an observation of his own. Haruka had noticed that it wasn’t just Nagisa that Rin was good at avoiding, it was entire crowds. He had seen Rin effortlessly navigate his way through festival mobs and swim meet crowds without so much as brushing a stranger’s shoulder. 

Haruka decided it wasn’t necessary to mention that he purposefully followed Rin through crowds so he wouldn’t have to deal with all the pushing and shoving either.

Makoto offered their next hint, recalling how accurate Rin had been on the rare occasions that they played Marco Polo or Shark in the Water as kids. Apparently Rin had been extremely good at finding the other kids when he was it, even if he stayed underwater. Both Haruka and Nagisa confirmed this, with much good natured grumbling from Nagisa. Rin had been extraordinarily good at locating the other kids in the pool.

Ironically, the final piece of evidence had been unwittingly provided by Rin himself. During a game of Truth or Dare at a sleepover at Makoto’s house he revealed the stupidest thing he did in Australia. The redhead detailed how he took a dare to grab onto an electric fence. According to Rin, the electric fence would switch back and forth between being safe and being charged full of electricity. When it was time for Rin to act out his dare, he had held his hand over the fencing, waited until his gut said it felt right, and grabbed hold. According to Rin he must’ve been lucky that night, because it was switched off when he touched it, but the other four exchanged a glance that said they clearly thought it was something more.

The next time the Iwatobi team had lunch, Rei spent it pouring through his book. With a triumphant shout he told them he’d figured it out. He took great delight explaining how sharks had additional senses that allowed them to pinpoint other creatures by sensing vibrations in the water and electrical signals.

Of course, this left them all with one burning question. Was Rin _really_ some kind of shark-person hybrid?

  
  
  
  


**5\. Floating on His Back:**

The last straw in the officially named “Shark-boy Rin Theory” came after another joint practice. The Samezuka team had already been dismissed to cooldown, leaving their captain to finish with the Iwatobi team. It didn’t take long for him and Makoto to discuss their takeaways from the last hour and hash out the details for the next joint practice, which meant they were able to spend a little time just relaxing in the pool.

It was always nice to get some pool time to themselves. Just goofing off in the pool brought back the fraughtless feel of childhood days, far from teenage stress and responsibilities.

Conversation drifted easily from topic to topic, mostly swimming related, before settling on preferred strokes. 

“I mean, I can do backstroke,” Rin was saying as he tread water, “but all the time?”

He shook his head.

“Why not?” Rei asked from the poolside.

Rin shrugged.

“I don’t know, I just kind of zone out during backstroke.”

“Really?” Makoto asked, treading water at Rin’s side. “Not that I’m looking for a face off, but I can’t imagine you zoning out during any competition no matter the stroke.”

Rin’s smile turned a little bashful.

“Thanks, Makoto,” he said, “but it’s true. I usually only do backstroke when I’m trying to relax.”

There was an ominous disturbance in the water behind them.

“Now we know how to make Rinrin... chill out!” Nagisa shouted, springing from the water and grabbing Rinks shoulders to pull the redhead back. There was a moment of much shouting, laughing, flailing, and splashing before quiet descended on the pool. 

Nagisa had managed to pull Rin onto his back before he could recover from the surprise, but now that he’d been released Rin made no move to right himself.

The last of Nagisa’s giggles faded.

“Okay Rinrin, I’m done now,” he said, regarding his prone friend.

Still, Rin remained where he was, floating effortlessly on the surface of the pool.

Nagisa traded a look with Makoto who swam closer. It was decidedly odd. Haruka even paused the laps he’d been swimming to come close enough to get a look.

“Rin?” Makoto asked, before waving a hand in front of Rin’s face.

The only sign Rin was aware of anything was the way he blinked as a few drops of pool water landed on his face, otherwise his expression remained the same; mouth slightly open as he stared unfocused at the ceiling above.

“This is so weird…” Nagisa commented.

Haru poked Rin’s side a few times to similar non-effect. 

“Really weird,” Makoto echoed.

“You don’t think…” Nagisa trailed off before turning to Rei, who was leaning over as far as he could without actually sliding back into the pool.

“Tonic immobility,” he said firmly. “A state of extreme relaxation bordering on a trancelike state sharks experience when flipped on their backs.”

“Whoa,” Nagisa murmured, speaking for the group as a whole.

“Rin _is_ a shark,” Haru concluded.

“Or a hybrid of some kind,” Rei added reasonably, “He can’t breathe underwater, after all.”

They shared a moment of silent consideration as their revelation sunk in.

“How do you think it happened?” Nagisa finally asked, imaginings of a young Rin in some mad scientist’s lab running through his head.

“I think we shouldn’t leave him like this too long,” Makoto replied, not wanting to admit to the images of shark demon curses floating through his own head.

Then he gently turned Rin’s shoulder until Rin was no longer prone and jolted back life.

He spluttered and fell right back into a rant as if his extended trance hadn’t even occurred.

“The heck, Nagisa?” Rin shouted, going a bit red faced.

Nagisa just laughed it off.

The whole while, Haruka was wondering how a shark and a human managed to fall in love.

  
  
  
  


**+1. Conservation:**

They lived with the knowledge of their friend’s strange… condition for several weeks before anything really came of it. Sure, Rin might have noticed some increased intensity in his friends’ stares when they were at the pool or out for a bite to eat, but if so he did he didn’t bring it up.

The truth was they really didn’t know what to do with their discovery. It wasn't the kind of thing you went out and told the world, not unless they wanted (more) mad scientists involved, and when they tried to bring it up to Gou she just gave them a look like she thought they’d ingested too much pool water.

There weren’t even any good books they could reference on the care and keeping teenage shark-boys to figure out if there was anything Rin needed. 

So they might know about the situation, but how to handle it was a complete mystery.

Their call to action came in the form of a panicked Nagisa bursting into the pool’s enclosure shouting, “Rinrin can’t go back to Australia!”

Freezing where he was attempting to sneak into the pool before warm-ups, Haruka’s head snapped toward Nagisa. 

“Rin’s going back to Australia?” he asked sharply.

In a mess of distressed confusion, he, Makoto, and Rei clambered for answers while Nagisa caught his breath. If Gou had been there yet, she probably could have cleared some of it up, but as it stood they just had to wait for Nagisa to get his voice back.

Finally, Nagisa got out, “No, I don’t think so, but the point is we can’t let him.”

There was a collective sigh of relief before Makoto guided Nagisa to a bench.

“Okay, deep breath, now why can’t Rin go to Australia?” he asked much more calmly.

“It’s terrible,” Nagisa replied gravely. “Australia is killing all of the sharks they can.”

He fished his phone out of his pocket to show them an article about an Australian shark cull.

“See? Australia’s not safe for sharks, so it can’t be safe for shark-boys either,” he insisted.

“This is serious,” Rei agreed. He put a hand to his chin in thoughtful consideration and allowed Haruka to take the phone.

“But what can we do about it?” Makoto asked, finding himself rather disturbed. The ocean was dangerous enough without big traps floating around. 

Haruka just studied the article carefully, letting plans flow around him.

……….

The following day brought Rin to Iwatobi’s grounds. Not for any reason related to the swim team, for once, just to pick up his sister.

And yet, Rin found himself staring at the Iwatobi swim team in utter bewilderment.

They had a booth. A booth with a group of students around it, and a hand drawn sign of a very muscular Iwatobi-chan holding a tearful shark.

They were shouting something he couldn’t make sense of, but honestly, he wasn’t sure if he wanted to.

So he just stood there, staring, until Gou got out of class and elbowed him in the gut.

“Hello! Earth to Rin!”

Rin shook himself.

“Sorry, I’m just…” he looked back at the booth where Rei and Nagisa were waving a clipboard in a classmate’s face, “What are they doing now?”

His sister just sighed, rolling her eyes at her team’s antics.

“Honestly, I’m not sure how it happened,” she sighed, “It’s like they all turned into zealous conservationists overnight.”

“Huh.” Rin commented, “That’s kind of random.”

The pair watched Makoto guilt trip a group of underclassmen into signing the form Haruka was stoically holding out to them. The man was so kind, he probably didn’t even realize he was doing it.

“Yeah, they’ve got a petition started about a shark cull in Australia,” Gou explained, “I hadn’t even heard about it until today.”

“Me neither,” Rin replied, still watching the busy little booth.

The little group of students from earlier had given up their signatures for the cause, and Makoto was turning to draw in another unsuspecting classmate. In the brief lull, Haru happened to glance up. His eyes met Rin’s, and a moment of silent acknowledgement passed between them before Haruka gave him a thumbs up.

Rin wasn’t sure what that was about, but he smiled back anyways.

Seemingly pleased, Haruka nodded before turning back to the job of collecting more signatures. 

“Well, I guess there’s worse things they could get into,” Rin said shaking his head before turning to Gou. “Come on, I promised you food.”

And with that, the pair left the Iwatobi team to their crusade for shark rights, neither knowing just what had prompted their protective frenzy.

  
  
  
  


**Bonus:**

Rin’s shark-boy status didn’t make too much of a change in the long run. He was still Rin, the overly emotional dreamer they’d known since childhood.

Still, it did make for an interesting topic of conversation.

“So if Rin-chan is part shark, what kind of shark is he?” Nagisa wondered aloud while he and the rest of the team waited for Rin to meet up with them.

It had been several weeks since their petition was completed and mailed to Australia.

“Not this again,” Gou sighed. In the ensuing weeks she had heard more about the shark-boy theory than she wanted to. It wasn’t like they were suggesting she was a shark-girl too, after all.

“No it’s a good question,” Rei replied. “There are just so many different kinds of sharks, it’s going to be hard to narrow it down.”

“I’m sure there’s some kind of clue we can use to figure it out,” Makoto assured smoothly.

Before they could delve deeper into discussion, they were interrupted by the creak of gate hinges.

“Hey, sorry I’m late!” Rin called, jogging up to the group in a pair of obnoxiously loud animal print pants.

He couldn’t understand why his friends took one look at him and all said, “Tiger shark.”

  
  
  


The End.

  
  



End file.
